D-galactose-binding lectins induce a differential response of blood platelets

Platelets are strongly aggregated by 50 μg/ml of soybean agglutinin (SBA), $\text{Cytisus scoparius}$ agglutinin (CSA I), and peanut agglutinin (PNA). The effects of SBA, CSA I, and PNA require pretreatment of the platelets with neuraminidase and are inhibited by D-galactose. PNA is the only one of these lectins which simultaneously induces the secretion and the concomitant shape change of platelets. Cytochalasin B enhances the effect of PNA but is inactive with SBA and CSA I. Thus the saccharide specificity of the lectins does not determine the kind of the platelet response for which additional binding properties of these lectins may be crucial.